Preparation of palladium catalysts

ABSTRACT

Palladium complexes having the general formula Pd(R&#39;CO 2 ) 2  X where R&#39; is C 1  to C 10  alkyl or C 6  to C 10  aryl and X is a chelating ligand of formula (R 2 ) 2  PYP(R 2 ) 2  where the R 2  groups are independently selected from C 1  to C 4  alkyl, phenyl or alkoxy substituted phenyl, and Y is --(CH 2 ) n  -- where n=2 to 4 are provided. The complexes may be prepared by reacting the compounds Pd(R&#39;CO 2 ) 2  and (R 2 ) 2  PYP(R 2 ) 2  together in an aromatic solvent at a temperature of less than 60° C. in amounts such that the molar ratio of the two compounds is in the range 1.2:1 to 1:1.2.

The present invention relates to the preparation of certain palladiumcarboxylate complexes which are useful sources of catalysts for thesynthesis of linear alternating polymers of one or more olefins andcarbon monoxide.

J Chem Soc 3632 (1965) discloses the preparation of palladiumcarboxylates by either reaction of palladium (II) nitrate with thecorresponding carboxylic acid (e.g. acetic acid or propionic acid) or byan exchange reaction involving palladium (II) acetate and e.g. benzoicacid or trifluoroacetic acid. This paper also teaches that adducts offormula Pd(CH₃ CO₂)₂ (PPh₃)₂ or Pd(C₂ H₅ CO₂)₂ (PPh₃)₂ (where Ph=phenyl)can be prepared by reacting the corresponding palladium carboxylatePd(CH₃ CO₂)₂ or Pd(C₂ H₅ CO₂)₂ with triphenylphosphine in benzene. Theseadducts however are said to dissociate and decompose rapidly in warmsolvents.

In J Chem Soc Dalton (1982) 1109 palladium complexes of formula Pd(O₂CPh)₂ (PPh₃)₂ and Pd(O₂ CPh)₂ (Ph₂ PCH₂ CH₂ PPh₂) are reported alongwith their physicochemical properties. These complexes are prepared byreacting the corresponding palladium (o) complexes Pd(PPh₃)₄ or Pd(Ph₂PCH₂ CH₂ PPh₂)₂ with dibenzoyl peroxide at room temperature.

EP 121965 and EP 181014 exemplify mixing palladium acetate with1,3-bis(diphenylphosphine)propane in methanol in the molar ratio 1:1.5.The product of these reactions is however not a simple palladium complexof the type described above.

It has now been found that palladium complexes having the generalformula Pd(R'CO₂)₂ X where R' is C₁ to C₁₀ alkyl or C₆ to C₁₀ aryl and Xis a chelating ligand of formula (R²)₂ PYP(R²)₂ where the R² groups areindependently selected from C₁ to C₄ alkyl or phenyl or phenylsubstituted with a polar group and Y is --(CH₂)_(n) --, where n=2 to 4,or a substituted derivatives thereof can of prepared by reacting theprecursors Pd(R'CO₂)₂ and (R²)₂ PYP(R²)₂ together in a suitable solvent.Furthermore, it is our belief that certain of these palladium complexesare new and we have determined that they are effective sources ofcatalysts for copolymerising mixtures of one or more olefins and carbonmonoxide to produce polyketones.

According to the present invention there is provided palladium complexeshaving the general formula Pd(R'CO₂)₂ X where R' is C₁ to C₁₀ alkyl orC₆ to C₁₀ aryl and X is a chelating ligand of formula (R²)₂ PYP(R²)₂where the R² groups are independently selected from C₁ to C₄ alkyl orphenyl or phenyl substituted with a polar group and Y is --(CH₂)_(n) --,where n=2 to 4, with the proviso that when R' is phenyl at least one R²group is other than phenyl.

The palladium complexes of the present invention may be prepared in theform of the monohydrate in substantially pure crystalline form by theprocess which will be described further below.

As regards the chelating ligand X, it is preferred that this is suchthat the R² groups are either all methyl or all aryl with chelatingligands in which the R² groups are phenyl or phenyl groups which are C₁to C₄ alkoxy substituted at the ortho position being most preferred. TheY group is most preferably selected from --(CH₂)₃ -- and --(CH₂)₄ --. Itis preferred that R' is C₁ to C₄ alkyl.

The palladium complexes of the present invention are easily prepared byreacting the compounds Pd(R'CO₂)₂ and (R²)₂ PYP(R²)₂ together is anaromatic hydrocarbon which is liquid at or below 60° C. Examples of sucharomatic hydrocarbons include benzene, toluene, one or more of theisomers of xylene and mesitylene. If the palladium complex is to beisolated, rather than used in situ, it is preferable to avoid the use ofsolvent such as methanol since this causes slow reduction of thecomplex. The molar ratio of the two precursors should be in the range1.2:1 to 1:1.2 and the reaction should be carried out at a temperaturebelow 60° C. to prevent decomposition of the product to metallicpalladium.

Using the precedure described above it will be found that the reactantswill initially dissolve in the solvent but that as reaction proceeds thepalladium complex will precipitate out. The palladium complex can beseparated from the reaction medium at the end of the reaction period byfiltration and washed with fresh solvent to produce analytically purematerial. Recrystallisation of the crude product can thereafter becarried out if it is so desired.

The palladium complexes of the present are useful sources of catalystsfor copolymerising mixtures of one or more olefins with carbon monoxideto produce linear polymers comprised of --Z-- and --CO-- units where Zis a divalent group corresponding to the particular olefin or olefinsused. A preferred method of using such a complex comprises dissolving itin an aliphatic alcohol solvent such as methanol or ethanol togetherwith 1 to 50 equivalents of an acid such as p-toluenesulphonic acid,trifluoromethanesulphonic acid trifluoroacetic acid or boroasalicylicacid and thereafter contacting the solution with one or more olefins,suitably C₁ to C₁₀ alpha olefins preferably e.g. ethylene, propylene ormixtures thereof, and carbon monoxide at a temperature in the range 20°to 200° C. and 1 to 100 bar gauge. Further details of this process canbe found in for example EP 121965 and EP 181014 the contents of whichare herein incorporated by reference.

The invention will now be illustrated by the following Examples.

EXAMPLE 1 Preparation of Pd(CH₃ CO₂)₂ (Ph₂ P(CH₂)₃ PPh₂) H₂ O

A filtered solution of 1,3-bis(diphenylphosphino)propane (1.85 g, 4.49mmol) in toluene (100 cm³) was added with stirring to a filterd solutionof palladium (II) acetate (1.00 g, 4.46 mmol) in toluene (25 cm³) over aperiod of five minutes. After stirring at room temperature for thirtyminutes, the reaction medium was filtered and the filtrate washed withfresh toluene (10 cm³). The filtrate was dried in vacuo to give thedesired product as a pale yellow powder. Yield 4.497 g (88%) ¹ H NMR(CH₃ OD solvent): 7.3-8.1 (20H, m), 2.8-3.1 (4H, m), 2.1-2.4 (2H, m),1.5 (6H, s). IR (KBr disc): V_(asym) (OCO)=1585 cm⁻¹, V_(sym) (OCO)=1372cm⁻¹.

Elemental analysis: Found: C, 56.7; H, 5.3. Calculated for C₃₁ H₃₄ O₅ P₂Pd: C, 56.8; H 5.2.

EXAMPLE 2 Use of the Complex in Preparing Polyketones

A carbon monoxide/ethene/propene terpolymer polyketone was prepared bythe following method.

The precursor palladium complex of Example 1 (0.0131 g, 0.0207 mmol),together with 1,4-benzoquinone (0.3525 g 3.264 mmol), hydrogenbis(5-chlorosalicylato) borate (0.5207 g, 1.404 mmol), propylene (28.60g, 0.68 mol) and methanol (100 cm³) were mixed in a 300 cm³ mechanicallystirred autoclave. An equimolar mixture of ethylene and carbon monoxidewas introduced such that the overall pressure was 33 bar g. The contentsof the autoclave were brought to 50° C. and the overall pressureadjusted to 50 bar g. These conditions were maintained for four hours byaddition of more of the gaseous mixture as appropriate. Thepolymerisation reaction was terminated by releasing the pressure. Thepolymer produced was collected by filtration, washed with acetone anddried in vacuo.

A yield of 11.3413 g of terpolymer polyketone was obtained.

I claim:
 1. Palladium complexes in substantially pure crystalline form having the general formula Pd(R'CO₂)₂ X where R' is C₁ to C₁₀ alkyl to C₆ to C₁₀ aryl and X is a chelating ligand of formula (R²)₂ PYP(R²)₂ where the R² groups are independently selected from C₁ to C₄ alkyl, phenyl or phenyl substituted with a polar group, and Y is --(CH₂)_(n) -- where n=3 or 4 with the proviso that when R' is phenyl at least one R² group is other than phenyl.
 2. Palladium complexes as claimed in claim 1 wherein at least one R² group is a phenyl group which is C₁ to C₄ alkoxy substituted at the ortho position.
 3. Palladium complexes as claimed in claim 2 wherein R¹ is C₁ to C₄ alkyl.
 4. A process for preparing a palladium complex having the general formula Pd(R'CO₂)₂ X where R' is C₁ to C₁₀ alkyl or C₆ to C₁₀ aryl and X is a chelating ligand of formula (R²)₂ PYP(R²)₂ where the R² groups are independently selected from C₁ to C₄ alkyl, phenyl or phenyl substituted with a polar group and Y is --(CH₂)_(n) where n=2 to 4 which process comprising reacting the compounds Pd(R'CO₂)₂ and (R²)₂ PYP(R²)₂ together is an aromatic solvent at temperature of less than 60° C. in amounts such that the molar ratio of the two compounds is in the range 1.2:1 to 1:1.2.
 5. A process as claimed in claim 4 wherein the aromatic solvent is selected from benzene, toluene, one or more of the isomers of xylene and mesitylene. 